EP1841170B1 - Learning address binding expiry time in an address translation device for a SIP signalling server - Google Patents

Learning address binding expiry time in an address translation device for a SIP signalling server Download PDF

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Publication number
EP1841170B1
EP1841170B1 EP06300303A EP06300303A EP1841170B1 EP 1841170 B1 EP1841170 B1 EP 1841170B1 EP 06300303 A EP06300303 A EP 06300303A EP 06300303 A EP06300303 A EP 06300303A EP 1841170 B1 EP1841170 B1 EP 1841170B1
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European Patent Office
Prior art keywords
client
messages
translation device
signaling server
address translation
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German (de)
French (fr)
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EP1841170A1 (en
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Thomas Levy
Gaelle Jaupitre
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Alcatel Lucent SAS
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Alcatel Lucent SAS
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Priority to DE602006017508T priority Critical patent/DE602006017508D1/en
Application filed by Alcatel Lucent SAS filed Critical Alcatel Lucent SAS
Priority to AT06300303T priority patent/ATE484911T1/en
Priority to EP06300303A priority patent/EP1841170B1/en
Priority to CN2007800111093A priority patent/CN101411162B/en
Priority to US12/224,870 priority patent/US8391291B2/en
Priority to PCT/FR2007/050972 priority patent/WO2007113426A1/en
Priority to JP2009502163A priority patent/JP4801198B2/en
Priority to KR1020087023985A priority patent/KR101247470B1/en
Publication of EP1841170A1 publication Critical patent/EP1841170A1/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L61/00—Network arrangements, protocols or services for addressing or naming
    • H04L61/09—Mapping addresses
    • H04L61/25—Mapping addresses of the same type
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L61/00—Network arrangements, protocols or services for addressing or naming
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
    • H04L65/1066—Session management
    • H04L65/1069—Session establishment or de-establishment
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
    • H04L65/1066—Session management
    • H04L65/1073—Registration or de-registration
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
    • H04L65/1066—Session management
    • H04L65/1101—Session protocols
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
    • H04L65/1066—Session management
    • H04L65/1101—Session protocols
    • H04L65/1104—Session initiation protocol [SIP]

Definitions

  • the present invention relates to the transmission of multimedia streams by a data communication network. It is particularly applicable to Internet Protocol (IP) telephony, IP videophony, etc.
  • IP Internet Protocol
  • the terminals In order for the signaling servers to have sufficient knowledge of the communication network, the terminals must register with their signaling server. In this way, each signaling server knows the terminals attached to it and the signaling messages (and calls) can be properly transmitted through the communication network. Such a record is typically performed by the registration message "Register” of the SIP protocol. This protocol also includes a message named "Prompt" that allows the calling party to initiate a session with a called party.
  • the global communication network (commonly referred to as the "Internet") can be seen as an interconnection of private communication networks.
  • These private networks can be, for example, corporate communication networks. They are connected together via one or more communication networks managed by communication operators.
  • NAT Network Address Translation
  • IETF RFC 3022 IP address Translation
  • NAPT Network Address and Port Translation
  • NAT also covers NAPT devices or other similar devices: bidirectional NAT, NAPT redirection of incoming flows (" NAPT Redirect / Port Forwarding "), NAT " double "(" Twice-NAT ”) etc.
  • the address translation device has a set of public addresses, usually in a much smaller number than the terminals connected to the private network. When one of these terminals wishes to access the public network, the NAT address translation device assigns him a public address among those still available in his game of public address. In the context of a Network Address and Port Translation (NAPT) , it can use the same public address for several private addresses. In this case, the association is made not only on the basis of the IP addresses but also on the ports used or other information (protocols etc.). This association between private and public coordinates is carried out temporarily. From the point of view of the public network, this terminal then has the public coordinates assigned by the NAT address translation device (or NAPT ...) and its private coordinates are then transparent to the public network.
  • NAPT Network Address and Port Translation
  • This association (or binding, " binding " in English) is necessarily temporary, so as not to monopolize the public addresses of the set of public addresses. Also, after a certain lapse of idle time, the association is terminated and the public address allocated becomes available again for a new mapping. This non-use occurs, for example, when a Transport Communication Protocol (TCP) connection is terminated between parties on either side of a NAT address translation device. When it is terminated, and after this lapse of time, called the expiration time, the association is terminated and if both parties wish to communicate again, they will need to establish a new association.
  • TCP Transport Communication Protocol
  • This aspect of the operation of an address translation device is for example explained in the " NAT Behavioral Requirements of Unicast UDP " document, published in September 2006 and available on the IETF website.
  • the Applicant has noticed that this will pose a growing problem with the increasing use of the SIP protocol for setting up multimedia sessions. Since this SIP protocol is based on UDP, the absence or insufficiency of signaling traffic during a multimedia session causes the session to be interrupted by the termination of the association of the NAT address translation device. Currently, this problem is partially solved by manually setting the validity period of the SIP signaling messages so that clients re-register at a period of time less than the NAT translation device timeout. Indeed, the SIP protocol provides that customers only register temporarily with a signaling server.
  • the registration message "Register” thus includes a parameter allowing the validity period to be specified beyond which the signaling server interrupts its "connection" with the client. Also, if the client wants to remain constantly connected with the signaling server, and accessible by the entire communication network, it must periodically re-issue registration messages "Register".
  • an access server instructs a SIP client to send periodic messages to maintain the connection at the NAT device.
  • This period of validity is usually negotiated between the client and the signaling server, but it can also be manually set by the operator.
  • This validity period of the SIP signaling messages can be set to a deliberately short value, in order to guarantee the non-termination of the association of the NAT address translation device.
  • the operator can also rely on the manufacturer data of the NAT address translation device, or carry out a statistical study, in order to determine a more optimal value of the validity period better in relation to the expiration time of this device.
  • the present invention proposes to solve these problems, by adapting the signaling server so that it automatically determines an optimum value of the expiration time of the signaling device. address translation, and for it to apply it as a period of validity of SIP protocol "Register" registration messages.
  • the automatic determination makes it possible to avoid the use of a human operator, and to reduce both the costs and the sources of error. It also allows a better optimization of the duration of validity which allows the ideal compromise between the non-termination of the association of the address translation device and the load of the communication network.
  • the messages of responses to the recording messages contain a validity slightly longer than the waiting time before the next test message is issued.
  • the learning phase ends when no response is received to a test message.
  • the test messages are "Options” messages.
  • the response messages may be "200 Ok” messages and the validity periods may be contained in an "Expires” field of these messages, or in an "Expires” parameter of a "Contacts” field of these messages.
  • Terminal means any communication equipment for establishing a multimedia session, that is to say voice over IP, video-voice etc. It may be a mobile terminal, compliant with UMTS ( Universal Mobile Telecommunications System ) or GPRS ( Global Packet Radio System ) standards for example, or a personal digital assistant (PDA for Personal Digital Assistant), a microcomputer, a device such as those sold by the company Blackberry TM etc. In the vocabulary specific to the SIP protocol, these terminals are considered as clients. In the following, the terms "customer” and "terminal” will be considered equivalent.
  • This second terminal (or client) is typically connected to another private network, also not shown.
  • the public network PUB comprises an SS signaling server which allows the routing of the signaling messages exchanged between the parties.
  • the figure 1 essentially illustrates the part of the architecture of the communication networks that connect this signaling server SS and a communication terminal T.
  • the two PRI and PUB communication networks are interconnected by (at least) a NAT address translation device.
  • the signaling messages exchanged between the terminal T and the signaling server SS are therefore transmitted through this NAT address translation device.
  • NAT address translation device In the private PRI network, terminals and nodes have addresses allocated independently of the global network. In other words, there is no guarantee that an address has already been assigned elsewhere in the world.
  • the purpose of the NAT address translation device is to isolate the PRI private network by ensuring that the private addresses are never used in communications with the public network PUB.
  • the NAT address translation device has a set P (or "pool” in English) of public addresses available at 1 , a 2 , a 3 . These addresses, which can be used throughout the public PUB network, are provided by the Internet Assigned Numbers Authority (IANA), which is the organization in charge of the development of addressing plans and the unique assignment of public addresses within the public network.
  • IANA Internet Assigned Numbers Authority
  • the signaling server SS assigns it one of the addresses available at 1 in the set P of public addresses, and in the case of a device of NAPT type, a port. This association is stored in an association table M (for "Map" in English).
  • the address translation device also has MT translation means to translate the fields of the IP packets relating to the coordinates of the terminal T in both directions, and to adjust the fields of correction codes (" checksum ") accordingly.
  • the packets from the terminal T will have, at the output of the NAT address translation device, the source address a 1 .
  • packets from the signaling server SS and addressed to this terminal T will have addresses of destination ⁇ 1 ; the only one known to this server.
  • the translation means MT of the NAT address translation device then use the correspondence table M to modify the fields so that the packets exit through the interface of the private network PRI with the address of destination, the private address ⁇ T . These packets can then be properly routed within the private network PR1 to the destination terminal T.
  • the NAT address translation device also has a counter allowing it to measure the time during which an association is not used. When this timeout expires, the association ends.
  • the figure 2 illustrates the signaling message flows between the parties to the communication.
  • This figure has a time axis oriented downwards.
  • Each vertical line is representative of a network element: the leftmost line represents the terminal T, the middle line the NAT address translation device and the right line, the SS signaling server.
  • the horizontal arrows represent the signaling messages.
  • these signaling messages can be of different natures: "Register” registration messages, "Options” test messages, "200 Ok” answer messages, etc. and other types not used in the invention. From the point of view of the vocabulary, it is important to note that the "Options" signaling message is not usually a test message: it conveys this meaning only in the context of the present invention.
  • the first message is a registration message. According to the SIP protocol, this may be a "Register” message as described in paragraph 10 of RFC 3261 mentioned above.
  • This message enables the terminal T to make itself known to the signaling server SS so that it integrates it into its information base comprising all the terminals (more generally "SIP clients") known by this signaling server SS. .
  • This message includes a header including a set of mandatory fields.
  • a SIP message must include at least the following fields: "To”, “From”, CSeq ",” Call-ID “,” Max-Forwards "and” Via " .
  • a "Contact” field may be incorporated into the "Register” registration message.
  • the information contained in RFC 2361 relating to the various fields of the SIP protocol messages are within the reach of the person skilled in the art.
  • SIP clients i.e., the T-terminal
  • the T-terminal do not offer a validity period.
  • the signaling server SS On receipt of this register message "Register", the signaling server SS analyzes the fields of the message and can determine that the sending terminal T is located behind an address translation device. NAT. This determination can for example be made by analyzing the content of the "Via” field of the header. As explained in section 8.1.1.7 of RFC 3261, the "Via” field indicates the network nodes through which the message is transmitted. By analyzing the "Via" field or fields, it is quite possible to determine that a registration message has passed through a NAT address translation device, and even to know its address.
  • the signaling server SS detects that the client T is located behind a NAT address translation device, an learning phase of an optimal duration of validity is triggered.
  • the signaling server determines an approximation of the expiry time of the association by sending successive test messages with increasing delay until detection of the termination of the association.
  • the signaling server SS first responds to the registration message with a "200 Ok" response message specified in the SIP protocol by RFC 3261.
  • This response message has a validity period set to a first value of 1. .
  • This first value d 1 is fixed so that it is ensured that it is less than the expiration time of the association of the NAT address translation device. This value is deliberately low, for example of the order of 15 seconds.
  • the client T is thus instructed by this "200 Ok" response message that he must re-transmit a registration message "Register” after a delay d 1 .
  • the signaling server SS waits for a delay d 1 'slightly less than the first validity period d 1 before issuing a test message to the client T. More generally, throughout the learning phase, the recording message response messages contain a validity period slightly longer than the waiting time before the next test message is sent.
  • This test message aims to verify whether the association of addresses within the NAT address translation device is still active or not.
  • An “Options” message can be implemented by the SIP "Options" message that allows one party to request the capabilities of another party.
  • An “Options” message has the same fields as a “Register” registration message. It can also have a "Contact” field.
  • the test message is transmitted to the client T.
  • the client returns a message. response message "200 Ok" which, in turn, traverses the NAT address translation device before reaching the signaling server SS.
  • the latter is then informed that the association is still active within the NAT address translation device. It can then deduce that the timeout of the association is greater than the waiting time d 1 '. He can then test a higher value for this time.
  • the signaling server SS In response to the second registration message "Register", the signaling server SS responds with a response message "200 Ok” containing a validity period set at a second value d 2 , greater than the first value d 1 . In parallel, the signaling server SS waits for a period of 2 slightly lower than the second validity period d 2 before sending a test message to the client T, such a message "Options.” As before, if the association is still active within the NAT address translation device, the signaling server receives a "200 Ok" response message to its test message.
  • the signaling server SS On receipt of the third registration message "Register", the signaling server SS therefore responds with a response message "200 Ok" containing a validity period set at a third value d 3 , greater than the second value d 2 . At the same time, the signaling server SS waits for a delay of 3 'slightly less than the third validity period d 3 before sending a test message to the client T, for example an "Options" message.
  • this third delay is greater than the expiration time of the NAT address processing device.
  • the latter can not then transmit the test message "Options" to the client T. Therefore, the signaling server SS never receives a response message "200 Ok”.
  • the terminal T transmits a registration message "Register” which creates a new association public address / private address within the NAT address translation device. This registration message "Register” is then transmitted through the NAT address translation device to the SS signaling server.
  • the signaling server determines that since it has not received a "200 Ok” response message to its "Options" test message, the timeout of the NAT address translation device is less than the last tested value d 3 '. Specifically, it can determine that the approximate value for this expiration time is between the value d 2 'and the value d 3 '.
  • the increment is 10 seconds between two consecutive values. This is an example, however, and it is entirely possible to use other numeric values.
  • the learning phase ends when no response is received to a test message.
  • the signaling server SS can then consider that the previous value d 2 is the optimum value of the validity period of the registration messages "Register” and use it for the rest. It then responds to the registration message "Register” with the value d 2 . It will respond with this value to any new message "Register” from the same terminal T, in a step of use.
  • the signaling server SS thus has a table allowing it to associate with any NAT address management device, an approximate expiration time. This embodiment makes it possible to overcome the learning phases of these expiry times and to go directly to a usage step and thus to save network resources by decreasing the number of messages that are exchanged during the period. learning stage.
  • the signaling server can seek to further optimize the approximate value to be used as the period of validity of the registration messages "Register". It can then proceed by dichotomy and test waiting times and intermediate validity, until a sufficient approximation of the expiration time of the NAT address translation device. At this point only, it goes into a usage stage, where the value thus determined is used in its exchange with the customer.
  • the terminal T is not accessible by the communication network. Indeed, since the test message has a value greater than the expiration time of the address translation device, the terminal T is inaccessible until the next registration message "Register". Thus, if an invitation message "Invite" arrives at the signaling server to the client T, it will not be able to respond to it since at this point it is no longer connected to the client T. This lapse of time is however negligible if the increments between two consecutive values d i / d i + 1 are sufficiently small.
  • the signaling server re-routes this call to a voice server, informing the caller that the client T will be available in a few seconds.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Multimedia (AREA)
  • Business, Economics & Management (AREA)
  • General Business, Economics & Management (AREA)
  • Data Exchanges In Wide-Area Networks (AREA)
  • Telephonic Communication Services (AREA)
  • Small-Scale Networks (AREA)
  • Computer And Data Communications (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

The server detects whether a terminal (T) e.g. mobile telephone, is located behind an network address translation device (NAT). The server determines an approximate expiration delay for a temporary association of a public address to a private address of the terminal, in case of a detection that the terminal is located behind the device (NAT), by successive sending of test messages after a rising wait delay till the detection of the termination of the association. The server transmits the approximate expiration delay as a validity duration to the terminal. An independent claim is also included for a method for connecting a signaling server with a client through a network address translation device.

Description

La présente invention concerne la transmission de flux multimédias par un réseau de communication de données. Elle s'applique particulièrement à la téléphonie sur IP (Internet Protocol), à la vidéophonie sur IP, etc.The present invention relates to the transmission of multimedia streams by a data communication network. It is particularly applicable to Internet Protocol (IP) telephony, IP videophony, etc.

Ces applications nécessitent le plus souvent l'établissement d'une session entre les parties. Ces parties sont le plus souvent des terminaux multimédia comme des terminaux de télécommunication (terminaux GSM, UMTS etc.), des assistants numériques personnels (PDA pour Personal Digital Assistant), des ordinateurs etc.
Cette session est établie par une partie dite « appelante » qui « invite » d'autres parties à joindre la session. Les invitations, ainsi que d'autres messages de signalisation, sont habituellement véhiculées par un protocole de signalisation comme le protocole SIP (Session Initiation Protocol) défini par le RFC 3261 de l'IETF (Internet Engineering Task Force).
Ces messages de signalisation SIP sont transmis à travers le réseau de communication à l'aide de serveurs de signalisation, communément appelés « proxy servers ». Ces serveurs de signalisation ont pour but principal d'interpréter les adresses contenues dans les messages de signalisation afin de les adresser à la partie destinatrice.These applications most often require the establishment of a session between the parties. These parts are most often multimedia terminals such as telecommunication terminals (GSM terminals, UMTS etc.), personal digital assistants (PDAs ), computers, etc.
This session is established by a so-called "appellant" party that "invites" other parties to join the session. Invitations, as well as other signaling messages, are usually conveyed by a signaling protocol such as the Session Initiation Protocol (SIP) defined by RFC 3261 of the Internet Engineering Task Force (IETF).
These SIP signaling messages are transmitted through the communication network using signaling servers, commonly called " proxy servers ". These signaling servers have the main purpose of interpreting the addresses contained in the signaling messages in order to address them to the destination party.

Afin que les serveurs de signalisation puissent disposer de la connaissance suffisante du réseau de communication, les terminaux doivent s'enregistrer auprès de leur serveur de signalisation. De cette façon, chaque serveur de signalisation connaît les terminaux qui lui sont rattachés et les messages de signalisation (et les appels) peuvent être convenablement transmis à travers le réseau de communication. Un tel enregistrement est typiquement effectué par le message d'enregistrement « Register » du protocole SIP.
Ce protocole comporte également un message nommé « Invite » qui permet à la partie appelante d'initialiser une session avec une partie appelée.In order for the signaling servers to have sufficient knowledge of the communication network, the terminals must register with their signaling server. In this way, each signaling server knows the terminals attached to it and the signaling messages (and calls) can be properly transmitted through the communication network. Such a record is typically performed by the registration message "Register" of the SIP protocol.
This protocol also includes a message named "Prompt" that allows the calling party to initiate a session with a called party.

Le réseau global de communication (que l'on nomme communément « Internet ») peut être vu comme une interconnexion de réseaux privés de communication. Ces réseaux privés peuvent être par exemple des réseaux de communication d'entreprise. Ils sont connectés ensemble via un ou plusieurs réseaux de communication gérés par des opérateurs de communication.The global communication network (commonly referred to as the "Internet") can be seen as an interconnection of private communication networks. These private networks can be, for example, corporate communication networks. They are connected together via one or more communication networks managed by communication operators.

Très souvent, les réseaux privés et le réseau public sont connectés par un dispositif de traduction d'adresses, nommé NAT (Network Address Translation) et décrit dans le RFC 3022 de l'IETF. Le but d'un tel dispositif est d'établir une association entre les adresses privées, d'usage uniquement interne au réseau privé, et des adresses publiques qui sont utilisés au sein du réseau public.
Parmi ces dispositifs NAT, il existe également des dispositifs de traduction d'adresses et de ports (NAPT pour « Network Address and Port Translation ») qui considèrent en sus des adresses IP, les ports indiqués dans les paquets IP. Dans ce qui suit, pour la facilité de la lecture, on considérera que l'acronyme NAT recouvre également les dispositifs NAPT ou autres dispositifs similaires : NAT bidirectionnels, NAPT à redirection des flux entrants (« NAPT Redirect/Port Forwarding »), NAT « double » (« Twice-NAT ») etc.
Toujours par soucis de clarté, nous appellerons « coordonnées », l'ensemble des informations contenues dans les paquets IP qui sont utilisées par un dispositif de type NAT pour identifier un équipement ou une application (adresses IP, ports...).Very often, private networks and the public network are connected by an address translation device, named NAT ( Network Address Translation ) and described in IETF RFC 3022. The purpose of such a device is to establish an association between private addresses, for use only internal to the private network, and public addresses that are used within the public network.
Among these NAT devices, there are also Network Address and Port Translation (NAPT) devices which consider in addition to the IP addresses the ports indicated in the IP packets. In what follows, for the ease of reading, it will be considered that the acronym NAT also covers NAPT devices or other similar devices: bidirectional NAT, NAPT redirection of incoming flows (" NAPT Redirect / Port Forwarding "), NAT " double "(" Twice-NAT ") etc.
Always for the sake of clarity, we will call "coordinates", the set of information contained in the IP packets that are used by a NAT device to identify a device or an application (IP addresses, ports ...).

Le dispositif de traduction d'adresses dispose d'un jeu d'adresses publiques, habituellement en nombre beaucoup plus restreint que les terminaux connectés au réseau privé. Lorsqu'un de ces terminaux souhaite accéder au réseau public, le dispositif de traduction d'adresses NAT lui attribue une adresse publique parmi celles encore disponible dans son jeu d'adresse publique.
Dans le cadre d'un NAPT (Network Address and Port Translation), il peut utiliser une même adresse publique pour plusieurs adresses privées. Dans ce cas, l'association est effectuée non seulement sur la base des adresses IP mais également sur les ports utilisés ou autres informations (protocoles etc.). Cette association entre les coordonnées privées et publiques est réalisée, de façon temporaire. Du point de vue du réseau public, ce terminal possède alors les coordonnées publiques attribuées par le dispositif de traduction d'adresses NAT (ou NAPT...) et ses coordonnées privées sont alors transparentes pour le réseau public.
Cette association (ou liaison, « binding » en langue anglaise) est nécessairement temporaire, afin de ne pas monopoliser les adresses publiques du jeu d'adresses publiques. Aussi, après un certains lapse de temps d'inutilisation, l'association est terminée et l'adresse publique attribuée redevient disponible pour une nouvelle mise en correspondance.
Cette inutilisation survient par exemple lorsqu'une connexion TCP (Transport Communication Protocol) est terminée entre des parties de part et d'autre d'un dispositif de traduction d'adresses NAT. À sa terminaison, et après l'écoulement de ce lapse de temps, appelée délai d'expiration, l'association est terminée et si les deux parties souhaitent à nouveau communiquer, il leur faudra établir une nouvelle association. Cet aspect du fonctionnement d'un dispositif de traduction d'adresses est par exemple expliqué dans le document « NAT Behavioral Requirements of Unicast UDP », publié en septembre 2006 et disponible sur le site de l'IETF.The address translation device has a set of public addresses, usually in a much smaller number than the terminals connected to the private network. When one of these terminals wishes to access the public network, the NAT address translation device assigns him a public address among those still available in his game of public address.
In the context of a Network Address and Port Translation (NAPT) , it can use the same public address for several private addresses. In this case, the association is made not only on the basis of the IP addresses but also on the ports used or other information (protocols etc.). This association between private and public coordinates is carried out temporarily. From the point of view of the public network, this terminal then has the public coordinates assigned by the NAT address translation device (or NAPT ...) and its private coordinates are then transparent to the public network.
This association (or binding, " binding " in English) is necessarily temporary, so as not to monopolize the public addresses of the set of public addresses. Also, after a certain lapse of idle time, the association is terminated and the public address allocated becomes available again for a new mapping.
This non-use occurs, for example, when a Transport Communication Protocol (TCP) connection is terminated between parties on either side of a NAT address translation device. When it is terminated, and after this lapse of time, called the expiration time, the association is terminated and if both parties wish to communicate again, they will need to establish a new association. This aspect of the operation of an address translation device is for example explained in the " NAT Behavioral Requirements of Unicast UDP " document, published in September 2006 and available on the IETF website.

Un problème se pose avec le protocole SIP. En effet, celui-ci est basé sur le protocole de plus bas niveau UDP (User Datagram Protocol) qui, contrairement à TCP, n'implique pas l'établissement d'une connexion de bout en bout entre les parties. Avec l'utilisation du protocole TCP, il faut donc une action positive de la part d'une des parties pour interrompre la connexion TCP pour que l'association soit terminée au sein du dispositif de traduction d'adresses NAT. Mais avec l'utilisation du protocole UDP, l'association peut se terminer sans action positive, simplement par la non émission de paquets de données durant une période au moins égale au délai d'expiration.A problem arises with the SIP protocol. Indeed, it is based on the lowest level User Datagram Protocol (UDP) which, unlike TCP, does not imply the establishment of an end-to-end connection between the parties. With the use of the TCP protocol, therefore, a positive action on the part of one of the parties to interrupt the TCP connection is required for the association to be terminated within the NAT address translation device. But with the use of the UDP protocol, the association can end without positive action, simply by the non-transmission of data packets for a period at least equal to the expiration time.

La demanderesse a remarqué que cela posera un problème grandissant avec l'utilisation croissante du protocole SIP pour l'établissement de sessions multimédias.
Ce protocole SIP étant basé sur UDP, l'absence ou l'insuffisance de trafic de signalisation durant une session multimédia entraîne l'interruption de la session par la terminaison de l'association du dispositif de traduction d'adresses NAT.
Actuellement, ce problème est partiellement résolu par la fixation manuelle de la durée de validité des messages de signalisation du protocole SIP afin que les clients se re-enregistrent selon une périodicité inférieure au délai d'expiration du dispositif de traduction d'adresses NAT. En effet, le protocole SIP prévoit que les clients ne s'enregistrent que temporairement auprès d'un serveur de signalisation. Le message d'enregistrement « Register » comporte donc un paramètre permettant de préciser durée de validité au-delà de laquelle le serveur de signalisation interrompt sa « connexion » avec le client.
Aussi, si le client veut demeurer constamment connecté avec le serveur de signalisation, et accessible par l'ensemble du réseau de communication, il doit re-émettre périodiquement des messages d'enregistrement « Register ».The Applicant has noticed that this will pose a growing problem with the increasing use of the SIP protocol for setting up multimedia sessions.
Since this SIP protocol is based on UDP, the absence or insufficiency of signaling traffic during a multimedia session causes the session to be interrupted by the termination of the association of the NAT address translation device.
Currently, this problem is partially solved by manually setting the validity period of the SIP signaling messages so that clients re-register at a period of time less than the NAT translation device timeout. Indeed, the SIP protocol provides that customers only register temporarily with a signaling server. The registration message "Register" thus includes a parameter allowing the validity period to be specified beyond which the signaling server interrupts its "connection" with the client.
Also, if the client wants to remain constantly connected with the signaling server, and accessible by the entire communication network, it must periodically re-issue registration messages "Register".

Dans US 2005/0286519 A1 , un serveur d'accès indique à un client SIP d'envoyer des messages périodiques afin de maintenir la connexion au niveau du dispositif NAT.In US 2005/0286519 A1 , an access server instructs a SIP client to send periodic messages to maintain the connection at the NAT device.

Cette durée de validité est habituellement négociée entre le client et le serveur de signalisation, mais elle peut être également fixée manuellement par l'opérateur.
Cette durée de validité des messages de signalisation SIP peut être fixée à une valeur délibérément courte, afin de garantir la non terminaison de l'association du dispositif de traduction d'adresses NAT.
L'opérateur peut aussi se baser sur les données constructeurs du dispositif de traduction d'adresses NAT, ou procéder à une étude statistique, afin de déterminer une valeur plus optimale de la durée de validité mieux en rapport avec le délai d'expiration de ce dispositif.This period of validity is usually negotiated between the client and the signaling server, but it can also be manually set by the operator.
This validity period of the SIP signaling messages can be set to a deliberately short value, in order to guarantee the non-termination of the association of the NAT address translation device.
The operator can also rely on the manufacturer data of the NAT address translation device, or carry out a statistical study, in order to determine a more optimal value of the validity period better in relation to the expiration time of this device.

Ces procédés souffrent toutefois de graves inconvénients.These processes suffer, however, serious disadvantages.

Tout d'abord, ils nécessitent l'intervention manuelle de l'opérateur. Il s'agit là d'une tâche coûteuse pour l'opérateur et susceptible de provoquer des erreurs de configuration. Par exemple, si le dispositif de traduction d'adresses est changé, il faut penser à modifier la valeur de la durée de validité en fonction.
En outre, le choix d'une valeur trop faible pour la durée de validité des messages de signalisation SIP charge le réseau de communication par l'émission d'un nombre trop important de messages d'enregistrement « Register ».
Ces différents problèmes sont assez peu sensibles aujourd'hui, mais selon la demanderesse, seront amenés à prendre une importance plus cruciale à mesure que se développe l'utilisation du protocole SIP pour l'établissement de sessions multimédias.First of all, they require the manual intervention of the operator. This is a costly task for the operator and may cause configuration errors. For example, if the address translation device is changed, consider changing the value of the validity period accordingly.
In addition, the choice of a value too low for the validity period of the SIP signaling messages loads the communication network by the issuance of too many registration messages "Register".
These various problems are rather insensitive today, but according to the applicant, will be made to take a more crucial importance as the use of the SIP protocol for the establishment of multimedia sessions develops.

La présente invention propose de résoudre ces problèmes, en adaptant le serveur de signalisation pour qu'il détermine de façon automatique une valeur optimale du délai d'expiration du dispositif de traduction d'adresses, et pour qu'il l'applique comme durée de validité des messages d'enregistrement « Register » du protocole SIP.The present invention proposes to solve these problems, by adapting the signaling server so that it automatically determines an optimum value of the expiration time of the signaling device. address translation, and for it to apply it as a period of validity of SIP protocol "Register" registration messages.

Plus précisément, l'invention a pour objets un serveur de signalisation comprenant des moyens de transmission de messages de signalisation SIP avec un client à travers un dispositif de traduction d'adresses NAT réalisant une association temporaire d'une adresse publique à l'adresse privée dudit client. Ce serveur comporte des moyens pour recevoir des messages d'enregistrement provenant de ce client, et pour lui adresser une durée de validité au bout de laquelle il doit transmettre un nouveau message d'enregistrement au serveur de signalisation.
Selon l'invention, ce serveur de signalisation se caractérise en ce qu'il dispose :

  • de moyens pour détecter que le client est situé derrière un dispositif de traduction d'adresse NAT et,
  • pour, dans cette situation, déterminer le délai approximatif d'expiration de l'association temporaire par envoi successif de messages de test après un délai d'attente croissant jusqu'à détection de la terminaison de ladite association, et
  • des moyens pour, à l'issue de cette détermination, transmettre au client ce délai approximatif d'expiration comme durée de validité.
More specifically, the subject of the invention is a signaling server comprising means for transmitting SIP signaling messages with a client through a NAT address translation device performing a temporary association of a public address to the private address. said customer. This server comprises means for receiving registration messages from this client, and to send it a period of validity at the end of which it must transmit a new registration message to the signaling server.
According to the invention, this signaling server is characterized in that it has:
  • means for detecting that the client is located behind a NAT address translation device and,
  • to, in this situation, determine the approximate expiration time of the temporary association by sending successive test messages after an increasing waiting period until detection of the termination of said association, and
  • means for, at the end of this determination, to transmit to the customer this approximate expiration period as a period of validity.

Ainsi, la détermination automatique permet d'éviter l'utilisation d'un opérateur humain, et de réduire à la fois les coûts et les sources d'erreur. Elle permet aussi une meilleure optimisation de la durée de validité qui permet le compromis idéal entre la non-terminaison de l'association du dispositif de traduction d'adresses et la charge du réseau de communication.Thus, the automatic determination makes it possible to avoid the use of a human operator, and to reduce both the costs and the sources of error. It also allows a better optimization of the duration of validity which allows the ideal compromise between the non-termination of the association of the address translation device and the load of the communication network.

Selon une mise en oeuvre de l'invention, durant une phase d'apprentissage, les messages de réponses aux messages d'enregistrement contiennent une durée de validité légèrement supérieure au délai d'attente avant l'émission du prochain message de test.
Selon un mode de réalisation de l'invention, la phase d'apprentissage se termine lorsque aucune réponse n'est reçue à un message de test.
Selon un mode de réalisation, les messages de test sont des messages « Options ».
Enfin, les messages de réponse peuvent être des messages « 200 Ok » et les durées de validité peuvent être contenus dans un champ « Expires » de ces messages, ou dans un paramètre « Expires » d'un champ « Contacts » de ces messages.According to one embodiment of the invention, during a learning phase, the messages of responses to the recording messages contain a validity slightly longer than the waiting time before the next test message is issued.
According to one embodiment of the invention, the learning phase ends when no response is received to a test message.
According to one embodiment, the test messages are "Options" messages.
Finally, the response messages may be "200 Ok" messages and the validity periods may be contained in an "Expires" field of these messages, or in an "Expires" parameter of a "Contacts" field of these messages.

L'invention a également pour objet un procédé de connexion d'un serveur de signalisation avec un client à travers un dispositif de traduction d'adresses réalisant une association temporaire d'une adresse publique à l'adresse privée du client, consistant à transmettre des messages d'enregistrement du client vers le serveur de signalisation, et à adresser au client une durée de validité au bout de laquelle il doit transmettre un nouveau message d'enregistrement au serveur de signalisation. Ce procédé se caractérise en ce qu'il comporte en outre

  • une étape de détection, par le serveur de signalisation, que le client est situé derrière un dispositif de traduction d'adresse ; et
  • dans cette situation, une étape d'apprentissage consistant à déterminer le délai approximatif d'expiration de ladite association temporaire par envoi successif de messages de test après un délai d'attente croissant jusqu'à détection de la terminaison de l'association, et
  • une étape d'utilisation, à l'issue de cette détermination, consistant à transmettre au client ce délai approximatif d'expiration comme durée de validité.
The invention also relates to a method of connecting a signaling server with a client through an address translation device performing a temporary association of a public address to the client's private address, consisting in transmitting data. client registration messages to the signaling server, and to send the client a period of validity after which it must transmit a new registration message to the signaling server. This process is characterized in that it further comprises
  • a step of detection, by the signaling server, that the client is located behind an address translation device; and
  • in this situation, a learning step of determining the approximate expiration time of said temporary association by sending successive test messages after an increasing waiting time until detection of the termination of the association, and
  • a step of use, at the end of this determination, of transmitting to the customer this approximate expiration time as a period of validity.

L'invention et ses avantages apparaîtront de façon plus claire dans la description qui va suivre en liaison avec les figures annexées :

  • La figure 1 schématise l'architecture générale dans laquelle s'inscrit le serveur de signalisation selon l'invention.
  • La figure 2 représente les flux d'échanges entre les différentes parties à la communication, selon l'invention.
The invention and its advantages will appear more clearly in the description which follows in conjunction with the appended figures:
  • The figure 1 schematizes the general architecture in which the signaling server according to the invention is inscribed.
  • The figure 2 represents the flow of exchanges between the different parties to the communication, according to the invention.

Ainsi qu'indiqué précédemment, l'invention s'inscrit dans le cadre d'une session multimédia établie entre un terminal T, situé dans un réseau privé PRI et un second terminal non représenté situé. On entend par terminal tout équipement de communication permettant d'établir une session multimédia, c'est-à-dire de voix sur IP, de vidéo-phonie etc. Il peut s'agir d'un terminal mobile, conforme aux normes UMTS (Universal Mobile Telecommunications System) ou GPRS (Global Packet Radio System) par exemples, ou un assistant personnel numérique (PDA pour Personal Digital Assistant), un micro-ordinateur, un dispositif tel ceux vendus par la société Blackberry™ etc.
Dans le vocabulaire propre au protocole SIP, ces terminaux sont considérés comme des clients. Dans la suite, les termes « client » et « terminal » seront considérés comme équivalents.As indicated above, the invention is part of a multimedia session established between a terminal T, located in a private network PRI and a second terminal not shown located. Terminal means any communication equipment for establishing a multimedia session, that is to say voice over IP, video-voice etc. It may be a mobile terminal, compliant with UMTS ( Universal Mobile Telecommunications System ) or GPRS ( Global Packet Radio System ) standards for example, or a personal digital assistant (PDA for Personal Digital Assistant), a microcomputer, a device such as those sold by the company Blackberry ™ etc.
In the vocabulary specific to the SIP protocol, these terminals are considered as clients. In the following, the terms "customer" and "terminal" will be considered equivalent.

Ce second terminal (ou client) est typiquement connecté à un autre réseau privé, également non représenté. Dans le cas d'une conférence multi-partie, plusieurs autres terminaux peuvent être parties à la session multimédia.
Le réseau public PUB comporte un serveur de signalisation SS qui permet l'acheminement des messages de signalisation échangés entre les parties.
La figure 1 illustre essentiellement la partie de l'architecture des réseaux de communication qui relient ce serveur de signalisation SS et un terminal de communication T.This second terminal (or client) is typically connected to another private network, also not shown. In the case of a multi-party conference, several other terminals may be parties to the multimedia session.
The public network PUB comprises an SS signaling server which allows the routing of the signaling messages exchanged between the parties.
The figure 1 essentially illustrates the part of the architecture of the communication networks that connect this signaling server SS and a communication terminal T.

Les deux réseaux de communication PRI et PUB sont inter-connectés par (au moins) un dispositif de traduction d'adresses NAT. Les messages de signalisation échangés entre le terminal T et le serveur de signalisation SS sont donc transmis à travers ce dispositif de traduction d'adresses NAT.The two PRI and PUB communication networks are interconnected by (at least) a NAT address translation device. The signaling messages exchanged between the terminal T and the signaling server SS are therefore transmitted through this NAT address translation device.

Au sein du réseau privé PRI, les terminaux et noeuds disposent d'adresses attribuées indépendamment du réseau global. Autrement dit, aucune garantie n'est prise pour savoir si une adresse a déjà été attribuée ailleurs dans le monde. Le dispositif de traduction d'adresses NAT a pour but d'isoler le réseau privé PRI en faisant en sorte que les adresses privées ne soient jamais utilisées dans les communications avec le réseau public PUB.In the private PRI network, terminals and nodes have addresses allocated independently of the global network. In other words, there is no guarantee that an address has already been assigned elsewhere in the world. The purpose of the NAT address translation device is to isolate the PRI private network by ensuring that the private addresses are never used in communications with the public network PUB.

Le dispositif de traduction d'adresses NAT dispose d'un ensemble P (ou « pool » en langue anglaise) d'adresses publiques disponibles a1, a2, a3. Ces adresses, utilisables au sein de l'ensemble du réseau public PUB, sont fournies par l'IANA (Internet Assigned Numbers Authority) qui est l'organisme en charge de l'élaboration des plans d'adressage et de l'attribution unique des adresses publiques au sein du réseau public.
Lorsque le terminal T souhaite communiquer en dehors du réseau privé PRI, et le serveur de signalisation SS lui attribue une des adresses disponibles a1 dans l'ensemble P d'adresses publiques, ainsi que dans le cas d'un dispositif de type NAPT, un port. Cette association est mémorisée au sein d'une table d'association M (pour « Map » en langue anglaise).
Le dispositif de traduction d'adresses dispose en outre de moyens de traductions MT pour traduire dans les deux sens les champs des paquets IP relatifs aux coordonnées du terminal T, et pour ajuster en conséquence les champs de codes de correction (« checksum »). Ainsi, les paquets provenant du terminal T auront, en sortie du dispositif de traduction d'adresses NAT, l'adresses source a1. Inversement, les paquets provenant du serveur de signalisation SS et adressés à ce terminal T auront comme adresses de destination α1; la seule qui soit connue de ce serveur. Les moyens de traduction MT du dispositif de traduction d'adresses NAT utilisent alors la table de correspondance M pour modifier les champs de sorte que les paquets ressortent par l'interface du réseau privé PRI avec comme adresse de destination, l'adresse privée αT. Ces paquets peuvent alors être correctement acheminés au sein du réseau privé PRl jusqu'au terminal destinataire T.The NAT address translation device has a set P (or "pool" in English) of public addresses available at 1 , a 2 , a 3 . These addresses, which can be used throughout the public PUB network, are provided by the Internet Assigned Numbers Authority (IANA), which is the organization in charge of the development of addressing plans and the unique assignment of public addresses within the public network.
When the terminal T wishes to communicate outside the private network PRI, and the signaling server SS assigns it one of the addresses available at 1 in the set P of public addresses, and in the case of a device of NAPT type, a port. This association is stored in an association table M (for "Map" in English).
The address translation device also has MT translation means to translate the fields of the IP packets relating to the coordinates of the terminal T in both directions, and to adjust the fields of correction codes (" checksum ") accordingly. Thus, the packets from the terminal T will have, at the output of the NAT address translation device, the source address a 1 . Conversely, packets from the signaling server SS and addressed to this terminal T will have addresses of destination α 1 ; the only one known to this server. The translation means MT of the NAT address translation device then use the correspondence table M to modify the fields so that the packets exit through the interface of the private network PRI with the address of destination, the private address α T . These packets can then be properly routed within the private network PR1 to the destination terminal T.

Le dispositif de traduction d'adresses NAT possède en outre un compteur lui permettant de mesurer le temps durant lequel une association n'est pas utilisée. À expiration de ce délai d'expiration, l'association se termine.The NAT address translation device also has a counter allowing it to measure the time during which an association is not used. When this timeout expires, the association ends.

La figure 2 illustre les flux de messages de signalisation entre les parties à la communication. Cette figure possède un axe temporel orienté vers le bas. Chaque ligne verticale est représentative d'un élément de réseau : la ligne la plus à gauche représente le terminal T, la ligne du milieu le dispositif de traduction d'adresses NAT et la ligne de droite, le serveur de signalisation SS.
Les flèches horizontales représentent les messages de signalisation. Comme on le verra par la suite, ces message de signalisation peuvent être de différentes natures : des messages d'enregistrement « Register », des messages de test « Options », des messages de réponse « 200 Ok » etc. et d'autres types non utilisés dans l'invention. Du point de vue du vocabulaire, il est important de noter que le message de signalisation « Options » n'est pas en général un message de test : il véhicule cette signification uniquement dans le cadre de la présente invention.The figure 2 illustrates the signaling message flows between the parties to the communication. This figure has a time axis oriented downwards. Each vertical line is representative of a network element: the leftmost line represents the terminal T, the middle line the NAT address translation device and the right line, the SS signaling server.
The horizontal arrows represent the signaling messages. As will be seen later, these signaling messages can be of different natures: "Register" registration messages, "Options" test messages, "200 Ok" answer messages, etc. and other types not used in the invention. From the point of view of the vocabulary, it is important to note that the "Options" signaling message is not usually a test message: it conveys this meaning only in the context of the present invention.

Le premier message est un message d'enregistrement. Selon le protocole SIP, il peut s'agir d'un message « Register » tel que décrit au paragraphe 10 du RFC 3261 sus-mentionné.The first message is a registration message. According to the SIP protocol, this may be a "Register" message as described in paragraph 10 of RFC 3261 mentioned above.

Ce message permet au terminal T de se faire connaître du serveur de signalisation SS afin que celui-ci l'intègre dans sa base d'information regroupant l'ensemble des terminaux (plus généralement « clients SIP ») connus par ce serveur de signalisation SS.
Ce message comporte un entête comprenant un ensemble de champs obligatoires. Ainsi qu'indiqué au paragraphe 8.1 du paragraphe du RFC 3261, un message SIP doit comporter au moins les champs suivants : « To », « From », CSeq », « Call-ID », « Max-Forwards » et « Via ». En outre, un champ « Contact » peut être incorporé dans le message d'enregistrement « Register ». Les informations contenues dans le RFC 2361 relatives aux différents champs des messages du protocole SIP sont à la portée de l'homme du métier.This message enables the terminal T to make itself known to the signaling server SS so that it integrates it into its information base comprising all the terminals (more generally "SIP clients") known by this signaling server SS. .
This message includes a header including a set of mandatory fields. As stated in paragraph 8.1 of RFC 3261, a SIP message must include at least the following fields: "To", "From", CSeq "," Call-ID "," Max-Forwards "and" Via " . In addition, a "Contact" field may be incorporated into the "Register" registration message. The information contained in RFC 2361 relating to the various fields of the SIP protocol messages are within the reach of the person skilled in the art.

Le protocole SIP prévoit qu'une durée de validité du message d'enregistrement « Register » soit indiqué dans ce message. Il propose deux façons de préciser cette information :

  • la durée de validité peut être indiquée dans un champ supplémentaire nommé « Expires », décrit au paragraphe 20.19 du RFC 3261 ;
  • la durée de validité peut être indiquée dans un paramètre « Expires » du champ « Contact » ainsi que précisé dans les sections 10.2 et 20.10 de ce même RFC 3261.
The SIP protocol provides that a period of validity of the "Register" registration message is indicated in this message. He proposes two ways to clarify this information:
  • the period of validity may be indicated in an additional field named "Expires", described in paragraph 20.19 of RFC 3261;
  • the period of validity may be indicated in an "Expires" parameter of the "Contact" field as specified in sections 10.2 and 20.10 of this same RFC 3261.

Par défaut, les clients SIP (i.e. le terminal T) ne proposent pas de durée de validité.By default, SIP clients (i.e., the T-terminal) do not offer a validity period.

À la réception de ce message d'enregistrement « Register », le serveur de signalisation SS analyse les champs du message et peut déterminer que le terminal émetteur T est situé derrière un dispositif de traduction d'adresses NAT. Cette détermination peut par exemple être faite par l'analyse du contenu du champ « Via » de l'entête.
Ainsi qu'explicité au paragraphe 8.1.1.7 du RFC 3261, le champ « Via » indique les noeuds de réseau par lesquels le message est transmis. En analysant le ou les champs « Via », il est tout à fait possible de déterminer qu'un message d'enregistrement est passé par un dispositif de traduction d'adresses NAT, et même de connaître son adresse.On receipt of this register message "Register", the signaling server SS analyzes the fields of the message and can determine that the sending terminal T is located behind an address translation device. NAT. This determination can for example be made by analyzing the content of the "Via" field of the header.
As explained in section 8.1.1.7 of RFC 3261, the "Via" field indicates the network nodes through which the message is transmitted. By analyzing the "Via" field or fields, it is quite possible to determine that a registration message has passed through a NAT address translation device, and even to know its address.

Si le serveur de signalisation SS détecte que le client T est situé derrière un dispositif de traduction d'adresse NAT, une phase d'apprentissage d'une durée de validité optimale est déclenchée.If the signaling server SS detects that the client T is located behind a NAT address translation device, an learning phase of an optimal duration of validity is triggered.

Pour ce faire, le serveur de signalisation détermine une approximation du délai d'expiration de l'association par envoi successif de messages de test avec un délai croissant jusqu'à détection de la terminaison de l'association.To do this, the signaling server determines an approximation of the expiry time of the association by sending successive test messages with increasing delay until detection of the termination of the association.

Le serveur de signalisation SS répond tout d'abord au message d'enregistrement par un message de réponse « 200 Ok » spécifiée dans le protocole SIP par le RFC 3261. Ce message de réponse comporte une durée de validité fixée à une première valeur d1. Cette première valeur d1 est fixée de sorte qu'il soit assuré qu'elle soit inférieure au délai d'expiration de l'association du dispositif de traduction d'adresses NAT. Cette valeur est donc délibérément peu élevée, par exemple de l'ordre de 15 secondes.The signaling server SS first responds to the registration message with a "200 Ok" response message specified in the SIP protocol by RFC 3261. This response message has a validity period set to a first value of 1. . This first value d 1 is fixed so that it is ensured that it is less than the expiration time of the association of the NAT address translation device. This value is deliberately low, for example of the order of 15 seconds.

Comme pour le message d'enregistrement « Register », le message de réponse « 200 ok » peut contenir la valeur d1 en (au moins) deux emplacements différents, ouvrant la possibilité de deux modes de réalisation de l'invention :

  • Dans un premier mode de réalisation, la durée de validité est transmise dans le champ « Expires » du message de réponse « 200 Ok ».
  • Dans un seconde mode de réalisation, la durée de validité est indiquée dans un paramètre « Expires » du champ « Contact ».
As for the registration message "Register", the response message "200 ok" may contain the value d 1 in (at least) two different locations, opening the possibility of two embodiments of the invention:
  • In a first embodiment, the validity period is transmitted in the "Expires" field of the "200 Ok" response message.
  • In a second embodiment, the period of validity is indicated in an "Expires" parameter of the "Contact" field.

Le client T est donc instruit par ce message de réponse « 200 Ok » qu'il doit re-émettre un message d'enregistrement « Register » au bout d'un délai d1.
Parallèlement, le serveur de signalisation SS attend durant un délai d1' légèrement inférieur au premier délai de validité d1 avant d'émettre un message de test vers le client T.
Plus généralement, durant toute la phase d'apprentissage, les messages de réponses aux messages d'enregistrement contiennent une durée de validité légèrement supérieure au délai d'attente avant l'émission du prochain message de test.The client T is thus instructed by this "200 Ok" response message that he must re-transmit a registration message "Register" after a delay d 1 .
At the same time, the signaling server SS waits for a delay d 1 'slightly less than the first validity period d 1 before issuing a test message to the client T.
More generally, throughout the learning phase, the recording message response messages contain a validity period slightly longer than the waiting time before the next test message is sent.

Ce message de test vise à vérifier si l'association d'adresses au sein du dispositif de traduction d'adresses NAT est encore active ou non.This test message aims to verify whether the association of addresses within the NAT address translation device is still active or not.

Il peut être mis en oeuvre par le message « Options » du protocole SIP qui permet à une partie de requérir les capacités d'une autre partie.
Un message « Options » comporte les mêmes champs qu'un message d'enregistrement « Register ». Il peut également posséder un champ « Contact ».It can be implemented by the SIP "Options" message that allows one party to request the capabilities of another party.
An "Options" message has the same fields as a "Register" registration message. It can also have a "Contact" field.

Si l'association est encore effective au sein du dispositif de traduction d'adresses NAT entre les adresses publique et privée du client T, le message de test est transmis jusqu'au client T. À sa réception, celui-ci renvoie un message de réponse « 200 Ok » qui, à son tour, traverse le dispositif de traduction d'adresses NAT avant de parvenir au serveur de signalisation SS. Celui-ci est alors informé que l'association est toujours active au sein du dispositif de traduction d'adresses NAT. Il peut alors en déduire que le délai d'expiration de l'association est supérieur au délai d'attente d1'.
Il peut alors tester une valeur plus élevée pour ce délai.If the association is still effective within the NAT address translation device between the public and private addresses of the client T, the test message is transmitted to the client T. When it is received, the client returns a message. response message "200 Ok" which, in turn, traverses the NAT address translation device before reaching the signaling server SS. The latter is then informed that the association is still active within the NAT address translation device. It can then deduce that the timeout of the association is greater than the waiting time d 1 '.
He can then test a higher value for this time.

En réponse au second message d'enregistrement « Register », le serveur de signalisation SS répond par un message de réponse « 200 Ok » contenant une durée de validité fixée à une deuxième valeur d2, supérieure à la première valeur d1.
Parallèlement, le serveur de signalisation SS attend durant un délai d2' légèrement inférieur au deuxième délai de validité d2 avant d'émettre un message de test vers le client T, par exemple un message « Options ».
Comme précédemment, si l'association est toujours active au sein du dispositif de traduction d'adresses NAT, le serveur de signalisation reçoit un message de réponse « 200 Ok » à son message de test.In response to the second registration message "Register", the signaling server SS responds with a response message "200 Ok" containing a validity period set at a second value d 2 , greater than the first value d 1 .
In parallel, the signaling server SS waits for a period of 2 slightly lower than the second validity period d 2 before sending a test message to the client T, such a message "Options."
As before, if the association is still active within the NAT address translation device, the signaling server receives a "200 Ok" response message to its test message.

Il peut à nouveau incrémenter les valeurs des délais, sachant que délai d'expiration du dispositif de traduction d'adresses NAT est donc encore supérieur au délai d'attente d2'.It can again increment the values of the delays, knowing that the expiration time of the NAT address translation device is therefore still greater than the waiting time d 2 '.

À réception du troisième message d'enregistrement « Register », le serveur de signalisation SS répond donc par un message de réponse « 200 Ok » contenant une durée de validité fixée à une troisième valeur d3, supérieure à la deuxième valeur d2.
Parallèlement, le serveur de signalisation SS attend durant un délai d3' légèrement inférieur au troisième délai de validité d3 avant d'émettre un message de test vers le client T, par exemple un message « Options ».On receipt of the third registration message "Register", the signaling server SS therefore responds with a response message "200 Ok" containing a validity period set at a third value d 3 , greater than the second value d 2 .
At the same time, the signaling server SS waits for a delay of 3 'slightly less than the third validity period d 3 before sending a test message to the client T, for example an "Options" message.

Dans l'exemple illustré par la figure 2, on suppose que ce troisième délai est supérieur au délai d'expiration du dispositif de traitement d'adresses NAT. Ce dernier ne peut alors pas transmettre le message de test « Options » vers le client T. Par conséquent, le serveur de signalisation SS ne reçoit jamais de message de réponse « 200 Ok ».
Au bout du délai de validité d3, le terminal T transmet toutefois un message d'enregistrement « Register » qui crée une nouvelle association adresse publique/adresse privée au sein du dispositif de traduction d'adresses NAT. Ce message d'enregistrement « Register » est alors transmis à travers le dispositif de traduction d'adresses NAT jusqu'au serveur de signalisation SS.In the example illustrated by the figure 2 it is assumed that this third delay is greater than the expiration time of the NAT address processing device. The latter can not then transmit the test message "Options" to the client T. Therefore, the signaling server SS never receives a response message "200 Ok".
After the validity period d 3 , however, the terminal T transmits a registration message "Register" which creates a new association public address / private address within the NAT address translation device. This registration message "Register" is then transmitted through the NAT address translation device to the SS signaling server.

Lorsqu'il reçoit ce message d'enregistrement « Register », le serveur de signalisation détermine que puisqu'il n'a pas reçu de message de réponse « 200 Ok » à son message de test « Options », le délai d'expiration du dispositif de traduction d'adresses NAT est inférieur à la dernière valeur testée d3'. Plus précisément, il peut déterminer que la valeur approximative pour ce délai d'expiration est entre la valeur d2' et la valeur d3'.When it receives this registration message "Register", the signaling server determines that since it has not received a "200 Ok" response message to its "Options" test message, the timeout of the NAT address translation device is less than the last tested value d 3 '. Specifically, it can determine that the approximate value for this expiration time is between the value d 2 'and the value d 3 '.

Exemples numériquesNumerical examples

Les délais utilisés peuvent être conformes au tableau suivant : d1 = 15 secondes d1' = 10 secondes d2 = 25 secondes d2' = 20 secondes d3 = 35 secondes d3' = 30 secondes d4 = 45 secondes d4' = 40 secondes The deadlines used may be in accordance with the following table: d 1 = 15 seconds d 1 '= 10 seconds d 2 = 25 seconds d 2 '= 20 seconds d 3 = 35 seconds d 3 '= 30 seconds d 4 = 45 seconds d 4 '= 40 seconds

Selon cet exemple, l'incrément est de 10 secondes entre deux valeurs consécutives. Il s'agit toutefois d'un exemple et il demeure tout à fait possible d'utiliser d'autres valeurs numériques.According to this example, the increment is 10 seconds between two consecutive values. This is an example, however, and it is entirely possible to use other numeric values.

Selon une première mise en oeuvre de l'invention, la phase d'apprentissage se termine lorsque aucune réponse n'est reçue à un message de test. Le serveur de signalisation SS peut alors considérer que la valeur précédente d2 est la valeur optimale de la durée de validité des messages d'enregistrement « Register » et l'utiliser pour la suite. Il répond alors au message d'enregistrement « Register » avec la valeur d2.
Il répondra avec cette valeur à tout nouveau message « Register » provenant du même terminal T, dans une étape d'utilisation.According to a first implementation of the invention, the learning phase ends when no response is received to a test message. The signaling server SS can then consider that the previous value d 2 is the optimum value of the validity period of the registration messages "Register" and use it for the rest. It then responds to the registration message "Register" with the value d 2 .
It will respond with this value to any new message "Register" from the same terminal T, in a step of use.

De même il pourra utiliser cette même valeur d2 avec tout nouveau terminal se situant derrière le même dispositif de traduction d'adresses NAT sans déclencher une phase d'apprentissage du délai d'expiration. Selon ce mode de réalisation, le serveur de signalisation SS dispose donc d'une table lui permettant d'associer à tout dispositif de gestion d'adresses NAT, un délai d'expiration approximatif. Ce mode de réalisation permet de s'affranchir des phases d'apprentissage de ces délais d'expiration et de passer directement à une étape d'utilisation et donc d'économiser des ressources du réseau en diminuant le nombre des messages qui sont échangés durant l'étape d'apprentissage.Similarly it can use the same value d 2 with any new terminal located behind the same NAT address translation device without triggering a learning phase of the expiration time. According to this embodiment, the signaling server SS thus has a table allowing it to associate with any NAT address management device, an approximate expiration time. This embodiment makes it possible to overcome the learning phases of these expiry times and to go directly to a usage step and thus to save network resources by decreasing the number of messages that are exchanged during the period. learning stage.

Selon une seconde mise en oeuvre de l'invention, le serveur de signalisation peut rechercher à optimiser encore la valeur approximative à utiliser comme durée de validité des messages d'enregistrement « Register ». Il peut alors procéder par dichotomie et tester des durées d'attente et de validité intermédiaire, jusqu'à obtenir une approximation suffisante du délai d'expiration du dispositif de traduction d'adresses NAT. À ce moment uniquement, il passe dans une étape d'utilisation, où la valeur ainsi déterminée est utilisée dans son échange avec le client.According to a second implementation of the invention, the signaling server can seek to further optimize the approximate value to be used as the period of validity of the registration messages "Register". It can then proceed by dichotomy and test waiting times and intermediate validity, until a sufficient approximation of the expiration time of the NAT address translation device. At this point only, it goes into a usage stage, where the value thus determined is used in its exchange with the customer.

Selon l'invention, il existe donc un lapse de temps durant lequel le terminal T n'est pas accessible par le réseau de communication. En effet, dès lors que le message de test comporte une valeur supérieure au délai d'expiration du dispositif de traduction d'adresses, le terminal T est inaccessible jusqu'au prochain message d'enregistrement « Register ». Ainsi, si un message d'invitation « Invite » arrive au serveur de signalisation à destination du client T, il ne sera pas à même d'y répondre puisqu'il n'est à ce moment précis plus connecté au client T.
Ce lapse de temps est toutefois négligeable si les incréments entre deux valeurs consécutives di/di+1 sont suffisamment faibles.According to the invention, there is therefore a lapse of time during which the terminal T is not accessible by the communication network. Indeed, since the test message has a value greater than the expiration time of the address translation device, the terminal T is inaccessible until the next registration message "Register". Thus, if an invitation message "Invite" arrives at the signaling server to the client T, it will not be able to respond to it since at this point it is no longer connected to the client T.
This lapse of time is however negligible if the increments between two consecutive values d i / d i + 1 are sufficiently small.

Il peut toutefois être prévu que lors d'un appel vers ce client T durant ce lapse de temps, le serveur de signalisation re-achemine cet appel vers un serveur vocal, informant l'appelant que le client T sera disponible dans quelques secondes.It can however be expected that during a call to this client T during this lapse of time, the signaling server re-routes this call to a voice server, informing the caller that the client T will be available in a few seconds.

Claims (7)

  1. A signaling server (SS) comprising means for transmitting SIP signaling messages with a client (T) through an address translation device (NAT) temporarily binding a public address to the private address of said client, comprising means for receiving registration messages from said client and for sending said client a validity period at the end of Which said client must transmit a new registration message to said signaling server (SS), said server characterized in that it has means for detecting whether said client is located behind an address translation device (NAT) and for determining, if this is the case, the approximate expiry time of said temporary binding by successively sending test messages after an increasing wait period until the termination of said binding is detected, and means for, upon the completion of this determination, transmitting this approximate expiry time to said client as a validity period.
  2. A signaling server according to claim 1. wherein, during a learning phase, the reply messages for the registration messages contain a validity period slightly greater than the time to wait before sending the next test message.
  3. A signaling server according to claim 2, wherein the learning phase ends when a test message has received no reply.
  4. A signaling server according to any one of the preceding claims, wherein said test messages are "Options" messages.
  5. A signaling server according to any one of the preceding claims, wherein the reply messages to the registration messages are "200 OK" messages; said validity periods being contained within an "Expires" field, or in an "Expires" parameter of a "Contacts" field of said reply messages,
  6. A signaling server according to any one of the preceding claims, further comprising a table associating each address translation device (NAT) with an approximate expiry time so that, whenever it detects that a given client is located behind a given address translation device (NAT), it directly uses the approximate expiry time associated with said given address translation device in said table.
  7. A method for connecting a signaling server (SS) with a client (T) through an address translation device (NAT) temporarily binding a public address to the private address of said client, consisting of transmitting registration messages from said client to said signaling server, and for sending said client (T) a validity period at the end of which said client (T) must transmit a new registration message to said signaling server (SS), characterized in that it further comprises a step of said signaling server (SS) detecting whether said client (T) is located behind an address translation device (NAT) and for determining, if this is the case, the approximate expiry time of said temporary binding by successively sending test messages after an increasing wait period until the termination of said binding is detected, and means for, upon the completion of this determination, transmitting this approximate expiry time to said client as a validity period,
EP06300303A 2006-03-30 2006-03-30 Learning address binding expiry time in an address translation device for a SIP signalling server Active EP1841170B1 (en)

Priority Applications (8)

Application Number Priority Date Filing Date Title
AT06300303T ATE484911T1 (en) 2006-03-30 2006-03-30 LEARNING THE LOGOUT TIME OF AN ADDRESS CONNECTION IN AN ADDRESS TRANSLATION DEVICE FOR A SIP SIGNALING SERVER
EP06300303A EP1841170B1 (en) 2006-03-30 2006-03-30 Learning address binding expiry time in an address translation device for a SIP signalling server
DE602006017508T DE602006017508D1 (en) 2006-03-30 2006-03-30 Learn the logout time of an address connection in an address translation device for a SIP signaling server
US12/224,870 US8391291B2 (en) 2006-03-30 2007-03-21 Learning the expiry time of an address binding within an address translation device for an SIP signaling server
CN2007800111093A CN101411162B (en) 2006-03-30 2007-03-21 Learning address binding expiry time in an address translation device for a SIP signalling server
PCT/FR2007/050972 WO2007113426A1 (en) 2006-03-30 2007-03-21 Learning expiry time of an association of addresses in an address translation device for sip signaling server
JP2009502163A JP4801198B2 (en) 2006-03-30 2007-03-21 Method for learning completion time of address binding in address translation device for SIP signaling server
KR1020087023985A KR101247470B1 (en) 2006-03-30 2007-03-21 Learning expiry time of an association of addresses in an address translation device for sip signaling server

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ATE484911T1 (en) 2010-10-15
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US8391291B2 (en) 2013-03-05
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